Some cancers are caused by mutations that stop certain proteins from working. The inactivation of whát kind or protein could lead to cancer? to.
a. one that sped up the cell cycle b. one that slowed down the cell cycle
C .one that acted as a growth-promoting molecule
d. one that responded to growth promoting molecules

The inactivation of one protein that slow down the cell cycle could lead to cancer. (option b).

Explanation:

The cell cycle is the process a cell undergoes when it divides during its life. This process includes a control mechanism to prevent normal cells from replicating more than normal, called cell cycle regulation.

In oncogenesis - the formation of malignant tumours - many factors induce the abnormal growth of a tissue by the abnormal multiplication of the cells that form it, leading to cancer. One of these factors may be a mutation in the DNA that prevents the production of regulatory proteins.

The mutation that produces exaggerated cell growth -and which can eventually lead to cancer- can create defects in a specific regulatory protein that slow down the cell cycle, so that exaggerated and uncontrolled cell replication occurs.

Once a tumor tissue has formed, successive mutations will lead to a lack of cell differentiation, the property of forming blood vessels, the ability to invade tissue and lose its apoptosis mechanism, that characterizes cancer cells.

Learn more:

Cyclines in cell cycle regulation link